The present invention relates to a method and apparatus for making containers, especially for making boxes or packs which consist of carboard or the like. More particularly, the invention relates to improvements in a method and apparatus for making collapsible boxes or analogous containers which can be erected by deforming flat tubular preforms so as to convert the preforms into tubes having a polygonal (normally square or rectangular) cross-sectional outline. Still more particularly, the invention relates to improvements in a method and apparatus for converting blanks which consist of cardboard or another suitable sheet material into flat tubes by resorting to a transporting system which advances successive blanks along stationary guide means with mutually staggered folding edges and by deforming selected portions or panels of successive blanks so that the deformed panels overlie certain parts of the guide means.
German Pat. No. 598,819 discloses an apparatus which is designed to form flat tubular preforms for the manufacture of boxes, packs or other types of containers. The operation is continuous and involves the conversion of successive blanks into tubular preforms. The blanks are transported by endless conveyor belts along a plurality of discrete stationary guide rails and are engaged by stationary wire yokes or similar folding elements which cause successive blanks to assume the shape of flat tubes, i.e., the blanks are converted into preforms which can be erected to constitute containers having a polygonal cross-sectional outline. The preforms are introduced into and stacked in a magazine. The apparatus which is disclosed in the aforesaid German patent renders it possible to turn out large quantities of preforms per unit of time. However, the seams where the marginal portions of neighboring walls or panels of the preforms are bonded to each other are not always uniform, i.e., it happens again and again that the absence of predictable overlapping of neighboring panels or laps which adhere to certain panels results in the making of containers whose configuration deviates from the desired optimum shape. Moreover, the numerous guide rails which are used in the patented apparatus and around which portions of the blanks are folded to convert such blanks into preforms cannot be mounted in such a way as to ensure highly accurate guidance of moving blanks. This is due to the fact that only one side or end of each guide rail can be mounted in cantilever fashion.